Various kinds of discharge electrodes of this kind are known to the art, and can be classified under two separate groups. In the first category or group of electrodes there is employed a frame structure having attached to mutually opposing parts thereof a plurality of mutually parallel conductors, normally laid in a helical configuration, and the d.c. voltage is applied to the frame structure.
The upper part of the frame structure is normally held by a carrier means.
The other category, or group of discharge electrodes are designated "rigid discharge electrodes" which are self-supporting and comprise an elongated member having attached thereto a plurality of electrode parts which present one or more discharge electrode tips. These electrode parts are distributed along the rod-like member and extend beyond the outer defining surfaces thereof. A rigid or self-supporting transmission electrode of this kind is attached at its upper part to a carrier means.
The discharge electrode described and illustrated in U.K. patent specification 1 100 328 constitutes an example of such prior art discharge electrodes.